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General Disclaimer One Or More of the Following Statements May Affect General Disclaimer One or more of the Following Statements may affect this Document This document has been reproduced from the best copy furnished by the organizational source. It is being released in the interest of making available as much information as possible. This document may contain data, which exceeds the sheet parameters. It was furnished in this condition by the organizational source and is the best copy available. This document may contain tone-on-tone or color graphs, charts and/or pictures, which have been reproduced in black and white. This document is paginated as submitted by the original source. Portions of this document are not fully legible due to the historical nature of some of the material. However, it is the best reproduction available from the original submission. Produced by the NASA Center for Aerospace Information (CASI) r 40^4 ^I I d 9 , GPL' , 1TIONAL-WAVE BURSTS FROM THE NUCLEI OF DISTANT GALAXLFS AND QUASARS: *+ PRGPOSAL FOR DETECTION USING DOPPLER TRACKING OF INTERPLANETARY SPACECRAFT KIP S. THORNE Californi,% Ints_itute of Technology, Pasadena, California, U.S.A. and VLADIMIR B. BRAGINSKY 1 1 hystcs Faculty, Moscow State University, Moscow, U.S.S.R. (NASA-CR-145432) GRAVITATIONAL-WAVE BURSTS N76-10977 FROM THE NUCLEI OF DISTANT GALLXIES AND QUASARS: PROPOSAL FOR DETECTION USING 6 J^ DOPPLER TRACKING OF INTERPLANETARY Unclas SPACFCRAFT (California Inst. of Tech.) 17 p G3/93 39447 R p v19 5 Nq4 41 Supported in part by the Ministry of Higher Education, U.S.S.R.; and by the National Aeronau and Space Administration [NCR-05-002-2561 and the National Science Foundation [MPS75-013981, U.S.A. Based in part on lectures by V. B. Braginsky at Caltech, Stanford, L.S.U., M.I.T., and Princeton in October 1974, and by K. S. 'Thorne at the Symposium on Theoretical Principles in Astrophysics and Rela`i ity, Chicago, May 27, 1'.75 ABSTRACT It is likely that supermassive black holes (M - 10 6 to 1010 M0 ) exist in the nuclei of many quasars and galaxies. The collapse which forms these holes and subsequent collisions between them should produce strong, broad-hand bursts of gravitational waves: for a source of mass M at the Hubble distance of 10 10 light years, the dimensionless ampli'.ude would be h . 2 x 10-17 x (M/10 6 M0 ), and the duration of the burst would be T - ( 90 sec)x (M/10 6 M0 ). Such bursts might arrive at Earth as often as SO times per year--or as rarely as once each 300 years. The detection of such bursts may be possible within the next few years using dual-frequency doppler tracking of interplanetary spacecraft. Subjec t headings: galactic. nuclei - gravitation - quasistellar sources or objects - relativity i 1. SOURCES OF THE BURSTS When building models for the cores of quasars, of strong radio sources, and of active galactic nuclei, theorists typically conclude that, whatever may be in the core, it is likely to generate one or more supermassive black holes 10 (M 10 6 to 10 MQ ) in a time short compared to the age of the Universe. See, e.g., Lynden-Bell (1969), Wolfe and Burbidge (1!'70), Spitzer (1971), and Saslaw (1974, 1975). A typical scenario involves the collapse of supermassive stars, gas clouds, or star clusters to form holes, and perhaps subsequent collisions between holes. Each such collapse or collision involving masses M z! 10 6 Ma should produce a burst of gravitational radiation so strong, that it might be observable at Earth. However, in the alternative scenario of a single hole which forms small (M << 10 (' MO ) and then grows by gradual accretion, no strong burst of gravitational waves can be expected (Davis et al. 1971). There are so few quasars and galaxies in the Universe (- 10 t0 ), and each one can produce so few strong gravitational-wave bursts (perhaps ; 10) that to detec, several bursts per year, we must search for them Over the entire volume of the observable Universe. Most such bursts will probably come from a redshift z = 2.5, when the Universe was about 2 billion years old, since quasar activity seems to have peaked very sharply at that time (Schmidt 1970, 1972). II. MEAN TIME BETWEEN 13URSTS Tlie mean time At between such gravitational-wave bursts at Earth can be expressed in terms of: (i) the Hubble expansion rate and deceleration parameter 11 q of the Universe today (which we assume globally Friedmann with zero cosmological u constant); (ii) the redshift z = 2.5 at which most of the bursts were generated; (iii) the number density n o today of "centers" where bursts or'.ginated (each 1 center was probably a galactic nucleus); (iv) the mean number of bursts N generated in each center during its active life; and (v) the speed of light c: 1 [ 1 - q 0 + q 0 z - (1-q 0 )(1 + 2g0z)1/2J At R 4nR 2 n 0 Nc (H0/c)go2',1 + z) cf. equation (29.33)of Misner, Thorne, and Wheeler (1973)--cited henceforth as MI V. Becau-ie number densities of cosmological objects are usually computed using 11 0 - 100 km sec -1 Mpc -1 and q o - 1, we shall assume these parameters; throughout. The more modern values H o - 55 and q o << 0.5 (Sandage 1972; Gunn et al. 1974) would give values of At smaller by a factor of 3. With H 0 = 100, q o = 1, r - 'I.5 the time between bursts is At = (0.06 years) (n0/Mpc-3)-I N-1 (2) Various assumptions--each quite reasonabl y --lead to widely differing estimates of n 09 the density of burst centers. If nearly every quasar (radio-quiet or radio-loud) produced at ..east one black hole and accompanying burst, then n o is the density of dead quasars in the Universe: I 1 x ].0 -6 ^ 1 5,^ 0.8 x 10 -4 t _ t0 n liv4 (t) _ t^, o "( 10 dT - f P,3 Mpc3 tlife n0 p t life dt tlife M c3 ) 1 Here (t) is the comoving density of live quasars at time t with M V < -22 nlive as estimated by Schmidt (1970, 1972); is the mean lifetime of quasar activity tlife in each center; and t o is the present age of the Universe. Schmidt's evolution 5t/t it-5t/to law, 1 live °` 10 0 = C requires an upper limit tlife < t0/11.5; and a lower limit might be (typical size, 100 kpc, of extended radio-emitting t,JLife ' regions)/(typical velocity, U.i c, expected for expan::on of extended regions in models of radio sources) ` 3 x 106 yrs (cf. Longair, Kyle, and Scheuer 1973; Blandford and Rees 1974). 'Thus 1 x 10-3 Mpc -3 < n 0 5 0.2 Mpc -3 if all quasars wete bu r st centers. (3) Suppose, alternatively, that all galaxies with violently active nuclei produce supermassive holes and wave bursts during their violence. Presumably the violence seen in strong r;% dio galaxies is sufficient. This leads to an n roughly the U - same as for quasars (eq. [31) (Schmidt 1966, 1972). Presumably the violence of a Seyfert galaxy also qualifies. The number density of Seyferts active today is - 2 x 10 -4 Mpc -3 (Huchra and Sargent 1973 adjusted from If - 75 ► ) H o = 100). However, it is likely that Seyfert acti%ity is transient, and that in the past a large fraction of all spiral galaxies with M V < -19 experienced nuclear violence comparable to that in Seyferts (n 0.01 Mpc -3 ; Shapiro 1971). 0 - Arguments for such widespread violence in spirals include these: (i) Of all non-Virgo-cluster and non-local-group spiral galaxies with corrected recession velocities v < 1000 km/sec, - 10 per cent have small radio sources in their nuclei, and - 5 per cent are "optically active" in ways that could be remnants of earlier, more violent behavior (Ulrich 1974). (ii) The only big (M V < -19) spirals close enough to be studied from the ground with optical resolution < 10 pc are our galaxy and M31 (Andromeda); and they both exhibit peculiar nuclear activity: (a) both show radial gas outflows suggestive of violent nuclear explusions in the past, perhaps 10 5 years ago (Munch 1960, Rubin and Cord 1969, Sanders and Prendergast 1974, and references therein); (b) M31, as viewed by Stratoscope II (Light, Danielsen, and Schwarzszhild 1974), has a nucleus so compact (M - 5 x 10 7 M; scale height 0.5 pc) that all of its stars more massive than 2 MO may by now have sunk to the center, producing violence (cf. Spitzer and Schull 1975); (c) the central 3 pc of our own galactic nucleus contains a radio source with diameter 5 200 AU and luminosity = 10 33 erg/sec at v - 10 GHz (Lo et al. 1975), which coincides with a discrete near-infrared source (Becklin and Neugebauer 1975 source 16) that does not show CO absorption (Becklin, private communication) and that therefore could be a cluster of red dwarfs emitting Ltotal 10' L0 and congregating around 3 a supermassive black hole (Sanders and Lowinger 1.972); (d) one cannot rule out our nucleus containing a black hole of mass as large as 1 x 10 8 M0 (Sanders and Wrixon 1973). If, as suggested by these observations, most spiral galaxies in the Universe Have experienced enough nuclear violence in the past to produce supermassive holes and strung gravitational-wave bursts, n o may he as loge as 0.31 Mpc -3 .
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